Smooth scrolling/Test plan

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Enable Smooth scrolling

Feature Status Lead engineer QA Lead Status
Enable Smooth scrolling Landed Jared Wein Mihaela Velimiroviciu Signed-off for Fx 13


Smooth scrolling is the animated sliding effect when you roll the scrollwheel. Without it, the page jumps one or several lines at a time when scrolled. It's a subtle effect, but it makes it easier to follow content as it moves and is a more enjoyable effect. It also compares more closely to touch-based scrolling and so increases consistency across PCs and touch-based devices.


Test Cases

  • The test cases for this feature can be viewed in Litmus under Firefox::Aurora::Aurora Basic Functional Tests (BFTs)::FX Aurora BFTs - Smooth Scrolling or here. Will be soon updated.

Important Bugs

Implementation bug

  • 710372 - [snappy] smooth scrolling - NEW

Other bugs

  • bug 198964 - Enable smooth scrolling by default - VERIFIED FIXED
  • bug 725700 - Keyboard arrow keys and scrollbar buttons should have consistent scrolling distances - VERIFIED FIXED
  • bug 710373 - Pressing the vertical slider down arrow with smooth scrolling should move three lines instead of one - VERIFIED FIXED
  • bug 206438 - Smooth scrolling should use the 'smoothwheel' algorithm - VERIFIED FIXED
  • bug 736251 - smooth wheel precise scrolling isn't very responsive - VERIFIED (FX13)
  • bug 482057 - When the Ctrl+F Find bar is enabled and the Find text box is focused, smooth scrolling does not work - VERIFIED (FX13)
  • bug 737758 - Improve bug 206438 to also work on OSX and Linux - VERIFIED (FX13)
  • bug 702463 - Make smooth scrolling use the refresh driver notifications instead of using its own timer - RESOLVED FIXED (FX 15)
  • bug 675015 - Suppress synthetic mouse events due to scrolling until the scroll is complete - RESOLVED FIXED (FX12)
  • bug 752376 - Make scrollbox.ensureElementIsVisible() a no-op if it doesn't overflow to prevent layout flushes - ASSIGNED
  • P1 bug 728738 - glitch in the smooth scroll animation - NEW
  • P1 bug 629507 - Make keyboard scrolling the same speed as scroll-arrow scrolling - NEW
  • P1 bug 718453 - Sluggish scrolling on Beta languages site - NEW
  • P2 bug 675866} - Meta: scrolling complex pages like Engadget is consistently slower and jerkier than the competition - NEW
  • P2 bug 682221 - choppy scrolling on when articles are expanded - NEW
  • P2 bug 699144 - Scrolling new gmail is really slow - NEW
  • P2 bug 720384 - scroll restoration happens far too late - NEW
  • P2 bug 721570 - Bad scrolling performance on - NEW
  • P2 bug 725851 - Throttle/Coalesce Scroll events on OSX with the trackpad - NEW
  • P2 bug 728153 - smooth scrolling waits 16ms before doing anything - NEW
  • P3 bug 720459 - Janky scrolling at - NEW
  • bug 758967 - Disable smooth scrolling by default (at least on Windows XP) - NEW

Bugzilla query

Sign off Criteria

  • All the test cases were executed.
  • All the major bugs have been fixed.
  • All bug fixes are verified.


  • Firefox 13.0a2 (Aurora) sign-off - 2012-03-19
    • Verified option is available and enabled by default in preferences panel and about:config
    • Verified verticalScrollDistance is consistently applied to scrolling with arrow key and vertical scroll button
    • Verified smooth scrolling using spage bar, UP/DOWN key, vertical scroll buttons, mouse wheel, magic mouse
  • Firefox 13.0 beta 1 sign-off - 2012-04-27
  • Firefox 13 sign-off - 2012-06-4